士道は慌てて首を振った。いらぬことを言ってへそを曲げられてはことである。
Context: The boy 士道 was trying to persuade a girl. The girl hated men and didn’t want to talk with 士道. If 士道 said anything amiss, the girl would get sulky further.
Hi. What is the function or meaning of the bold part? Is it some fixed kind of grammar pattern?
Thank you.
